Nowadays, packaging containers of the single-use disposable type are often employed for packing and transporting foods of a liquid nature, such as milk. The material in these so-called single-use packages is normally composed of a plurality of mutually laminated layers of the same or different materials which, in cooperation with one another, impart the desired mechanical and chemical properties to the package.
A well-known packaging laminate which has long been employed in the art for this type of package consists, for example, of one or more inner layers of a fiber material, which gives the package the requisite mechanical strength and configurational stability, and outer layers of plastics which give the package its necessary tightness properties against liquids which could otherwise readily penetrate into the fiber layers of the packaging material and thereby weaken the mechanical strength and bond properties of the package. Preferably, the outer plastics layer of the packaging laminate consists of thermoplastic, ideally polyethylene, which is impermeable to liquid and moisture and which, moreover, makes the packaging laminate heat-sealable or fusible in such a manner that mutually facing plastics layers of the packaging laminate may readily be united to one another by surface fusion for the formation of mechanically strong, liquid-tight sealing joints or seams during the packaging production process.
Thus, from a web of the above-described prior art packaging laminate, there are produced configurationally stable, liquid-tight single use packages employing modern, rational packaging machines which reform the web into a tube, in that the two longitudinal edges of the web are brought to overlap one another and are fused to one another in a longitudinal lap joint or seam. The tube is filled with the desired contents and then divided into closed, cushion-shaped packages by repeated transverse sealings of the tube, transversely of the longitudinal axis of the tube, beneath the level of the contents in the tube. The packages are separated from one another by incisions in the transverse sealing zones and are given the desired geometric, normally parallelepipedic, final form by a subsequent forming and sealing operation.
Even if a packaging laminate of the above-outlined type with outer layers of thermoplastic functions satisfactorily in several respects, it nevertheless suffers from numerous serious drawbacks. Thermoplastics, for example polyethylene, are extracted from oil which is a non-renewable natural resource and consequently runs the long-term risk of becoming exhausted. At the same time, it is currently difficult (and in many cases impossible) to recover and recycle the thermoplastic in spent packaging laminates and used packages. Further, thermoplastics are plastics which are biologically difficult to degrade and, in order to counteract the growth of the much debated "refuse mountain", it is often necessary to incinerate the used packaging material, with other consequential environmental problems.